What other files are on the disk aside from .idx? Typically the .idx file is just used for indexing. So it would only contain partial data. I have an old rand mcnally file which has files like abc.idx and abc.mnt. The *.mnt files would usually be aroun 5 MB in size and the *.idx files only around 600KB. In this situation it is clear that the idx file is for indexing the larger file. Is the Lexus data similar? ArcView will expect the idx file to be an index of some other file. Is ArcView free?

The mappoint extraction looks promising.

Also, you could also build something to crawl websites and gather the info